Which Direction are Herbicides Heading? (image) University of Illinois College of Agricultural, Consumer and Environmental Sciences Share Print E-Mail Caption Auxinic herbicides like 2,4-D and dicamba trigger uncontrolled growth called epinasty in sensitive broadleaf weeds such as giant ragweed (Ambrosia trifida). Credit Photo by William Johnson, Purdue University, and provided by Dean Riechers, University of Illinois Usage Restrictions For use with U of I release titled, Share Print E-Mail Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.